Schneider Altivar 61 OBF Fault — What It Means
The OBF fault on the Schneider Electric Altivar 61 variable speed drive indicates motor overload — the drive’s thermal protection model has detected that the motor current has exceeded the programmed overload threshold for long enough to risk motor damage. The Altivar 61 is widely used in pump and fan HVAC applications; OBF is the motor thermal trip, distinct from OCF (overcurrent trip).
Common Causes
- Motor running at sustained overcurrent — A pump or fan with a heavy load running continuously near or above the motor FLA accumulates thermal count until OBF trips.
- ItH (motor thermal current) parameter set too low — If the motor thermal current parameter is set below the actual motor FLA, OBF trips prematurely under normal conditions.
- High ambient temperature in motor environment — Motors in hot spaces lose cooling effectiveness, drawing more current for the same torque output.
- Cooling fan failure on the motor — Forced-ventilated motors with a failed shaft fan overheat rapidly at full load, tripping OBF.
Step-by-Step Fix
- Check the motor thermal current parameter — On the ATV61 keypad, navigate to [MOTOR CONTROL] → [ItH] and verify it matches the motor nameplate FLA. Adjust to correct value if wrong.
- Measure motor current — Use the [MONITORING] menu to read output current during normal operation. Compare to motor nameplate FLA. Current at or above FLA during normal operation = mechanical overload or undersized motor.
- Inspect the load — Check pump for cavitation, blockage, or worn impeller. Check fan for debris on blades or damaged housing causing resistance.
- Check motor cooling — Confirm the motor ventilation path is clear and the cooling fan is running. Force-ventilated motors fail rapidly when cooling fails.
- Reset and monitor — Navigate to [FAULT RESET] to reset OBF. Monitor ItH accumulation (available in monitoring menu) over the next run cycle.
Parts Often Needed
| Part | Notes |
|---|---|
| Motor (if windings damaged) | Test winding resistance and insulation before replacement |
| Motor cooling fan | Replace if not running on force-ventilated motor |
Need Replacement Parts?
Finding the right replacement parts for your equipment is critical to getting it running again. Check current prices on Amazon — prices and availability change frequently.
When to Call a Pro
If OBF trips with correct parameters and no mechanical overload, the motor may be undersized for the application. Consult an Schneider application engineer for drive/motor sizing review.